The project will examine several aspects of intravenous drug self-administration in baboons. One area of study will be the development and refinement of procedures for measuring the relative reinforcing efficacy of drugs. Procedures to be examined include fixed-ratio schedules and multiple fixed-interval fixed-ratio schedules. Studies will involve both parametric manipulations and between-drug comparisons. Systematic comparisons of a series of anorectic stimulants will be undertaken. A second area of study will be an examination of pharmacological and environmental factors which interact with drug reinforcement. These studies will employ both multiple fixed-ratio schedules and choice procedures, and should provide information about mechanisms of drug reinforcement.